The present application claims priority under 35 U.S.C. xc2xa7119 to Korean Application No. 2001-34100 filed on Jun. 16, 2001, which is hereby incorporated by reference in its entirety for all purposes.
1. Field of the Invention
The present invention relates to an ashing apparatus for a semiconductor device, and more particularly, to an ashing apparatus by which ionized gases are poured into a chamber provided in a dry etching equipment and are uniformly diffused on wafers through ring-shaped pipes.
2. Description of the Related Art
Generally, semiconductor devices can be fabricated by combination of a great number of processes such as the formation of a thin film on a wafer, patterning of a thin film, a washing process, and the like. A process in which a photoresist remaining on a wafer after an etch process is removed is called an ashing process. The ashing process may be called a P/R strip process, which is a type of dry etch process.
In a common dry etching process, gases poured into a reaction chamber are changed into a plasma state by an electrical action such as a discharge, and wafers are etched by the plasma. In contrast, in an ashing process, ionized plasma only is selected from the whole plasma of reactive gases and ashing is performed by the ionized plasma, i.e., ion components. In such an ashing process, the ion components are created outside of a reaction chamber, and are guided into the internal portion of the chamber. An ashing process can be classified into multi-type and single-type ashing processes, according to the way the wafers are arranged to be processed in a chamber. The multi-type ashing process commonly includes accumulating and processing the wafers in batches.
FIG. 1 illustrates a conventional single-type process ashing apparatus, which will be briefly.explained as follows. In the single-type process semiconductor ashing apparatus, ions are injected into the reaction chamber 10 through an ion inlet (ion ejector)11, as shown in FIG. 1. Such an injection method is similar to the method in a multi-type process ashing apparatus, by which ions are created outside of the chamber and are injected into the chamber. That is, the ion inlet (ion ejector) 11 serves to guide only ion components out of plasma made in plasma quartz PQ, into chamber 10. The plasma is generated in the quartz that is placed outside of the chamber by a radio frequency power source (RF power source). The ions introduced into the chamber 10 flow through a gas diffuser plate 20 (GDP) which is formed with numerous through holes 21 and which serves to divide the internal space of the chamber into two spaces, i.e., the upper and lower spaces.
The GDP 20 is commonly made of quartz. The ions that pass through the GDP 20 are sprayed on a wafer 30 that is placed on the stage 40 in a lower side or space of the chamber 10. That is, the ions are injected into the reaction chamber 10 through the ion ejector 11, and the ions that pass through the ion ejector 11 are again passed through the GDP 20, thereby being sprayed on a wafer 30. At this time, the ions are uniformly sprayed on the wafer 30 due to the uniformly formed through holes 21.
The reason that the ion ejector 11 is formed at a sidewall of the chamber will be briefly explained as follows. In an ashing process, photoresist on a wafer should be in a softened state, so that ions properly react with the photoresist as well as the wafer. A hardened photoresist on the wafer will react weakly with ions, so that ashing cannot be effectively performed. Therefore, in order to make the photoresist soft, it is necessary to heat the photoresist at a predetermined temperature. To heat only the photoresist without affecting any other adjacent objects, a halogen lamp (not shown) is employed to heat the photoresist. The halogen lamp radiates light and the light serves to heat the photoresist on the wafer in the chamber. That is, the light radiated from the halogen lamp passes through the upper cover 12 formed of quartz and illuminates the inside of the chamber 10. The light is also radiated onto the wafer 30 after passing through the GDP 20, which is also made of quartz. As a result, the light serves to heat the photoresist on the wafer 30 due to the heat energy of the light, thereby softening the photoresist.
In such an environment, in order for the wafer to be directly contacted with the light radiated from the halogen lamp that is provided over the cover 12, intervening objects cannot be provided between the cover 12 and the wafer 30. For this reason, the ion ejector 11 through which the ions are passed should be formed at the sidewall of chamber 10, as shown in FIG. 1. However, there is a problem in such an apparatus in that since ions are injected into chamber 10 through ion ejector 11 provided at a sidewall of chamber 10, the portion of GDP 20 adjacent to the ion ejector 11 is provided with a relatively greater number of ions than a portion of GDP 20 that is placed far from the ion ejector 11. The ions passed through GDP 20 in such an environment cannot be uniformly distributed on a wafer.
In other words, a portion of wafer 30 nearer to the ion ejector 11 is provided with a relatively large amount of ions, as illustrated in FIG. 2. However, a portion of wafer 30 that is placed far from the ion ejector 11 is provided with a relatively small amount of ions. As a result, the distribution of ions on the wafer is not uniform, thereby causing the problem that ashing efficiency of a wafer decreases.
Particularly, there is also a problem that since the light radiated from the halogen lamp is transmitted both through the upper cover 12 made of quartz and the GDP 20 made of quartz, the transmissivity of light decreases. As a result, the heating rate of the photoresist by the transmitted light in chamber 10 accordingly decreases.
The present invention is therefore directed to an ashing apparatus which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
To solve the above noted problems, it is an object of the present invention to provide an ashing apparatus by which ions can be uniformly sprayed onto a wafer in a chamber through a ring shaped distribution pipe, thereby increasing ashing uniformity of a wafer.
It is another object of the present invention to provide an ashing apparatus in which light radiated from a halogen lamp can be transmitted through an upper cover only, to directly illuminate a wafer, thereby increasing heating efficiency and raising ashing efficiency of a wafer.
In order to achieve these objects, there is provided an ashing apparatus which includes a chamber; a plasma quartz in which plasma ions are generated; an inlet provided at a sidewall of the chamber through which the plasma ions are ejected into the chamber; a chamber upper cover made of quartz, through which light radiated from a halogen lamp is transmitted for ashing a wafer by heat of the light; and a ring shaped distribution pipe, coupled to the inlet and disposed along a circumference of an interior of the chamber, the ring shaped distribution pipe having a plurality of distribution holes through which the ions are directly sprayed onto the wafer.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.